Writing instrument case



FIG. 1 is a front perspective view of an ornamental design for a writing instrument case according to the present invention;

FIG. 2 is a partially open view of the case of FIG. 1;

FIG. 3 is a partially open view of the case of FIG. 1 showing an array of caps;

FIG. 4 is an open view of the case of FIG. 1;

FIG. 5 is a front view of the case of FIG. 1;

FIG. 6 is a rear view of the case of FIG. 1; and,

FIG. 7 is a top, open view of the case of FIG. 1.

The broken lines shown in FIGS. 1-7 are for the purpose of illustrating environmental structure and form no part of the claimed design. 

CLAIM The ornamental design for a writing instrument case, as shown and described. 